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Abstract

Two parallel combinative long-period fiber gratings (LPFGs) can convert the fundamental core mode LP01 in a single-mode fiber (SMF) into one desired higher order core mode LP0m in a few-mode fiber (FMF), in the process of which one specific cladding mode acts as a medium coupled from one fiber to another. Different LP0m modes can be obtained by controlling the grating period of LPFG in FMF to meet the phase matching condition. In this article we focus on the design and analyses of LP02 and LP03 mode add / drop multiplexers (MADMs). This device has some advantages of facile and good scalability, and particularly, of eliminating coupling interferences for the ahead multiplexed modes by the posterior MADMs or couplers. Furthermore, the conversion rate of mode power theoretically can approach as much as98%and the 3dB bandwidth can reach 10nm or more.

Figures (7)

Diagram of MADM and mode conversion from the fundamental mode LP01 to cladding
mode HE16 and then to HOMs LP02 and LP03, with their
transverse electric field distributions shown from left to right and up to down.

(a) Exchange relationship of mode power with coupling crosstalk from SMF to FMF. (b)
Coupling efficiency of respective LPFG in SMF and FMF. (c) Total conversion ratio of MADMs
for multiplexing LP02 and LP03 .